The present invention relates to a gateway apparatus and its address administration method whereby different networks of two kinds can be connected and devices on the networks can be assigned unique addresses. In particular, the present invention relates to gateway apparatuses whereby when devices of networks each including a gateway apparatus are connected, addresses can be assigned so as to avoid duplication between two gateway apparatuses.
In recent years, digitization of AV (audio-visual) devices represented by TVs and VTRs have been promoted. Digital satellite broadcast receivers, i.e., set top boxes (hereafter abbreviated to STBs), video cassette recorders (VCRs), video cameras and hard disks using a digital recording system, and recording apparatuses using an optical disk such as a DVD-RAM have made their appearance. Among these AV devices, there are increasing devices that adopt an IEEE 1394 serial bus (hereafter referred to as 1394 bus), whereby fast data communication of high quality can be conducted in connection with another AV device. The 1394 bus has a data transfer rate of a maximum 400 Mbps and an isochronous transfer mode whereby video and audio data can be transmitted in real time. In addition, the 1394 bus has an advantage that the user's operation can be reduced because insertion and removal of a cable are detected and a node ID having 16 bits is automatically assigned to each device. Therefore, attention has been paid to the 1394 bus as a standard interface of digital AV devices. Hereafter, an AV network using the 1394 bus is referred to as 1394 network.
On the other hand, in-home network construction has begun as well as a result of spread of information devices represented by PCs (Personal Computers) and the Internet. As one form of in-home networks, there can be mentioned an information system network that aims at sharing internet access and a printer among a plurality of PCs, such as notebook computers used by individuals and a desktop PC shared by family members. On this network, TCP/IP utilized on the Internet as a protocol is typically used, and an address called IP address is used to identify each device. At the present time, a version called IPv4 using a 32-bit address is the mainstream. In recent years, however, a new version expanded in address to 128 bits and called IPv6 (Internet Protocol version 6) has been drawn up.
As shown in FIG. 2, an IPv6 address 200 includes a network prefix 201 represented by 64 high-order bits thereof and an interface ID 202 represented by 64 low-order bits thereof. The network prefix 201 is used as an identifier of a connected network. A value notified of by a router by utilizing an automatic stateless address autoconfiguration function is set in the network prefix 201. The interface ID 202 is used as an identifier of a device that exists on the network. In the case of a LAN using a twist pair line, the interface ID 202 is set on the basis of a 48-bit MAC address. In the case of a 1394 bus, the interface ID 202 is set on the basis of a node unique ID (hereafter abbreviated to unique ID) having 64 bits. Hereafter, an information system network using the TCP/IP is referred to as IP network.
For exchanging data directly between a device on the IP network and a device on the 1394 network, a gateway apparatus having both interfaces in order to connect the two networks becomes necessary.
In JP-2001-202317, there is described a method of controlling a digital AV device or the like connected to a 1394 bus via such a gateway apparatus, by using a controller on the IP network.
According to the above described conventional technique, one gateway apparatus, which forms the nucleus in the home, has an address translation table that associates IP addresses and unique IDs previously provided to devices on the 1394 network with each other, and transmits data received from the IP network or the Internet to a device on the 1394 network on the basis of the address translation table.
In a system configuration in which two or more gateway apparatuses exist on an IP network and a 1394 network exists for each of the gateway apparatuses, a user connects a device on a 1394 network to a device on a different 1384 network by using a 1394 bus. Such a situation is conceivable. In this case, it turns out that devices that have existed on different 1394 networks exist on one 1394 network. User's operation of updating contents of address translation tables administered by the two gateway apparatuses so as not to cause duplication becomes necessary. Even in the case where the gateway apparatuses automatically update the address translation tables, a mechanism for preventing duplication of contents of address translation tables among a plurality of gateway apparatuses becomes necessary.